os: rework kernel architecture

Rework the code structure and architecture of the kernel by separating
platform-dependent and platform-independent code more cleanly. As of
this patchset, full feature parity has not been achieved. Nonetheless, a
sufficient subset of functionality has been ported to the new
architecture to demonstrate the feasibility of the new structure.

1 files changed, 84 insertions, 0 deletions

diff --git a/arch/x86_64/src/vga/text.cpp b/arch/x86_64/src/vga/text.cpp
new file mode 100644
index 0000000..c9eee71
--- /dev/null
+++ b/arch/x86_64/src/vga/text.cpp
@@ -0,0 +1,84 @@
+#include "x86_64/vga/text.hpp"
+
+#include "kapi/boot.hpp"
+
+#include "x86_64/boot/boot.hpp"
+#include "x86_64/boot/ld.hpp"
+#include "x86_64/vga/crtc.hpp"
+
+#include <algorithm>
+#include <bit>
+#include <cstddef>
+#include <cstdint>
+#include <span>
+#include <string_view>
+#include <utility>
+
+namespace teachos::vga::x86_64::text
+{
+  namespace
+  {
+    constexpr auto BUFFER_BASE_ADDRESS = std::uintptr_t{0xb8000};
+    constexpr auto DEFAULT_TEXT_BUFFER_WIDTH = 80U;
+    constexpr auto DEFAULT_TEXT_BUFFER_HEIGHT = 25U;
+    constexpr auto CURSOR_ENABLED_BIT = 5U;
+  }  // namespace
+
+  std::span<device::glyph> const device::buffer =
+      std::span{std::bit_cast<device::glyph *>(BUFFER_BASE_ADDRESS +
+                                               std::bit_cast<std::uintptr_t>(&teachos::boot::x86_64::TEACHOS_VMA)),
+                DEFAULT_TEXT_BUFFER_WIDTH * DEFAULT_TEXT_BUFFER_HEIGHT};
+
+  device::device()
+      : m_position{boot::bootstrap_information.vga_buffer_index}
+  {}
+
+  auto device::clear(attribute attribute) -> void
+  {
+    m_position = 0;
+    std::ranges::fill(buffer, std::pair{' ', std::bit_cast<std::byte>(attribute)});
+  }
+
+  auto device::cursor(bool enabled) -> void
+  {
+    auto cursor_disable_byte = std::byte{!enabled} << CURSOR_ENABLED_BIT;
+
+    crtc::address::write(crtc::registers::cursor_start);
+    crtc::data::write(crtc::data::read() | cursor_disable_byte);
+  }
+
+  auto device::newline() -> void
+  {
+    auto current_line = m_position / DEFAULT_TEXT_BUFFER_WIDTH;
+    auto next_line = current_line + 1;
+
+    if (std::cmp_greater_equal(next_line, DEFAULT_TEXT_BUFFER_HEIGHT))
+    {
+      auto begin = buffer.begin() + DEFAULT_TEXT_BUFFER_WIDTH;
+      auto end = buffer.begin() + DEFAULT_TEXT_BUFFER_WIDTH * DEFAULT_TEXT_BUFFER_HEIGHT;
+      std::ranges::move(begin, end, buffer.begin());
+      m_position = current_line * DEFAULT_TEXT_BUFFER_WIDTH;
+    }
+    else
+    {
+      m_position = next_line * DEFAULT_TEXT_BUFFER_WIDTH;
+    }
+  }
+
+  auto device::write(std::string_view code_points, attribute attribute) -> void
+  {
+    std::ranges::for_each(code_points, [&](auto code_point) -> void { write(code_point, attribute); });
+  }
+
+  auto device::write(char code_point, attribute attribute) -> void
+  {
+    buffer[m_position++] = std::pair{code_point, std::bit_cast<std::byte>(attribute)};
+  };
+
+  auto device::writeln(std::string_view code_points, attribute attribute) -> void
+  {
+    std::ranges::for_each(code_points, [&](auto code_point) -> void { write(code_point, attribute); });
+    newline();
+  }
+
+}  // namespace teachos::vga::x86_64::text